A purple acid phosphatase from sweet potato contains an antiferromagnetically coupled binuclear Fe-Mn center.

A purple acid phosphatase from sweet potato is the first reported example of a protein containing an enzymatically active binuclear Fe-Mn center. Multifield saturation magnetization data over a temperature range of 2 to 200 K indicates that this center is strongly antiferromagnetically coupled. Metal ion analysis shows an excess of iron over manganese. Low temperature EPR spectra reveal only resonances characteristic of high spin Fe(III) centers (Fe(III)-apo and Fe(III)-Zn(II)) and adventitious Cu(II) centers. There were no resonances from either Mn(II) or binuclear Fe-Mn centers. Together with a comparison of spectral properties and sequence homologies between known purple acid phosphatases, the enzymatic and spectroscopic data strongly indicate the presence of catalytic Fe(III)-Mn(II) centers in the active site of the sweet potato enzyme. Because of the strong antiferromagnetism it is likely that the metal ions in the sweet potato enzyme are linked via a mu-oxo bridge, in contrast to other known purple acid phosphatases in which a mu-hydroxo bridge is present. Differences in metal ion composition and bridging may affect substrate specificities leading to the biological function of different purple acid phosphatases.

Injection abscesses due to mycobacterium chelonei occurring in a diabetic patient.

The case of a young fit diabetic patient who suffered from injection abscesses is presented. Mycobacterium Chelonei var chelonei was the organism responsible. The organism was difficult to isolate, but skin tests yielded valuable results. The abscesses responded to treatment with erythromycin and cotrimoxazole.

Evaluation of buffy-coat microscopy for the early diagnosis of bacteraemia.

Three hundred and sixty samples of blood from 230 hospital patients were examined and compared with the results of simultaneous blood culture to determine the value of buffy-coat microscopy in detecting bacteraemia. One observer found 86 positive smears, 12 of which were from patients with positive blood cultures and 74 from patients with negative blood cultures. The buffy-coat smear was negative in 274 specimens, 8 of which yielded positive blood cultures. A second observer considered that only 34 of the buffy coats were positive. Only six of these were associated with positive blood cultures. Although there was a statistically significant association between positive smears and positive blood cultures, the procedure has little practical value because of the high incidence of false positives and negatives.

Carriage of group D streptococci in the human bowel.

Sixty faecal samples, 39 from adults and 21 from neonates, were investigated by means of a simple scheme to isolate and identify any group D streptococci present. A number of differences were found between the two groups. Group D streptococci were absent from 43% of the neonates compared with only 13% of the adults; Streptococcus bovis was commoner in the neonates (23.8%) than in the adults (5%), and Streptococcus faecium was not isolated from any of the infant samples although it was common in the adult samples (25%). The viable counts of Strep. faecium were found to be, on average, 100-fold lower than those of Streptococcus faecalis. The methods and results are discussed with reference to the clinical significance of group D streptococci, especially in bacterial endocarditis and carcinoma of the colon.